Refactor polyomino implementations (#201)

* add cspuz_rs/src/polyomino.rs

* use polyomino_placement in Statue Park solver

* move tetrominoes() and pentominoes() to polyomino.rs

* add tests

* format

* use polyomino_placement in Battleship solver

* factor out PieceCombinator

* factor out PiecesCombinator

Author: semiexp

cspuz_rs/src/lib.rs

@@ -4,6 +4,7 @@ pub mod complex_constraints;
 pub mod graph;
 pub mod hex;
 pub mod items;
+pub mod polyomino;
 pub mod serializer;
 pub mod solver;